Today blood treatment apparatuses are used for extracorporeal blood treatment and involves drawing blood from a patient, treating the blood and returning the treated blood to the patient. For this purpose an extracorporeal blood flow circuit is used which is connected to a blood vessel access of the patient, typically via one or more access devices such as needles or cannulas inserted into the blood vessel access. Depending on method of blood treatment, the blood may be withdrawn and returned via the same blood vessel access or via separate blood vessel accesses. Extracorporeal blood treatment includes hemodialysis, hemodiafiltration, hemofiltration, plasmapheresis etc.
The blood treatment apparatus is in principle an electrically powered machine that is fed with an electrical current. If an electrical failure occurs in the blood treatment apparatus, there might be a risk that the patient is subjected to an electrical shock which may have severe consequences. Thus, it is vital that the blood treatment apparatus is designed such that it offers a high degree of electrical insulation for reducing the risk that an electrical current flows from the apparatus, via the extracorporeal blood circuit and access device and into the patient.
This problem has been addressed, for example in WO2009/044220 A1 where a blood treatment apparatus includes a membrane device that comprises a blood chamber and a fluid chamber separated by a semipermeable membrane. A grounding device is connected to a treatment fluid discharge line by means of a tubular connector made of an electrically-conductive plastic material. The grounding device can disconnect the grounding connection if a leakage current measured on a patient connected to the apparatus exceeds a predetermined value.
Further prior art is reflected by US2009177149 A1 where various kinds of leakage currents are addressed, and by U.S. Pat. No. 4,155,852 A which relates to a blood treatment apparatus that incorporates an electrically isolated flux heater.
The techniques mentioned above are generally capable of reducing the risk of a patient being subject to an electrical shock. However, it is believed that the risk can be further reduced in case a blood treatment apparatus experiences an electrical failure. This is particularly relevant when the blood treatment apparatus is intended for home use, where relatively higher safety requirements typically are required.